Disposal of industrial and sanitary wastes

ABSTRACT

Sludges and other organic by-products of industrial and community activity which present difficulties due to the presence of dispersed solids can be put to useful purpose with concurrent recovery, in whole or part, of inherent fuel values. Upon injection of such by-products diluted with added water to a delayed coker as aqueous quench medium, water content of the sludge is utilized to cool the hot coke. The dispersed solids and any organic liquids present are apparently dispersed through the coke mass, contrary to the expectation that these contaminants would be filtered out on the surface of the coke face first contacted thereby. The combustible solid portions of the byproduct become a part of the primary fuel (coke). Non-combustible solids (e.g. sand, rust, silt) are distributed throughout the mass of coke in such manner that increase in ash content is acceptable as being within commercial specifications.

Unite States Patent [191 Meyers 1 Nov. 4, 1975 1 DISPOSAL OF INDUSTRIALAND SANITARY WASTES [75] Inventor: Robert L. Meyers, Beaumont, Tex.

[73] Assignee: Mobil Oil Corporation, New York,

[22] Filed: Aug. 7, 1974 [21] Appl. No.: 495,460

Primary ExaminerHerbert Levine Attorney, Agent, or FirmC. A. HuggettNophiho 8 Lighter /3 HCGO o, COMBINATION TOWER [57] ABSTRACT Sludges andother organic by-products of industrial and community activity whichpresent difficulties due to the presence of dispersed solids can be putto useful purpose with concurrent recovery, in whole or part, ofinherent fuel values. Upon injection of such byproducts diluted withadded water to a delayed coker as aqueous quench medium, water contentof the sludge is utilized to cool the hot coke. The dispersed solids andany organic liquids present are apparently dispersed through the cokemass, contrary to the expectation that these contaminants would befiltered out on the surfacev of the coke face first contacted thereby.The combustible solid portions of the byproduct become a part of theprimary fuel (coke). Non-combustible solids (e.g. sand, rust, silt) aredistributed throughout the mass of coke in such manner that increase inash content is acceptable as being within commercial specifications.

4 Claims, 1 Drawing Figure Clarification U.S. Patent Nov. 4, 1975 HHMOJ.NOILVNISWOQ %W m Ewcmn DISPOSAL OF INDUSTRIAL AND SANITARY WASTES FIELDOF THE INVENTION The invention is concerned with modification in twopreviously disparate industrial arts, namely l delayed coking of heavypetroleum fractions and (2) disposal of industrial and sanitary(biological) wastes.

SUMMARY OF THE PRIOR ART Delayed Coking. This refinery process is ameans for handling very high boiling, viscous residues resulting fromvarious petroleum refining unit processes. Such stocks are verydifficult to process in other types of processes, due at least in partto the very low ratio of hydrogen to carbon which is characteristic ofthese stocks. Their use directly as fuel is restricted due to the factthat they cannot be pumped except at elevated temperatures or afterdilution with lighter fractions of much greater value such as kerosinesand light gas oils, thereby degrading the value of the cutter stock".

The coker is therefore a means for converting low value by-products ofpetroleum refining into salable solid coke and light liquid products bya thermal cracking operation. Viewed another way, it aids in achievingstoichiometric balance in a refinery between the crude and desiredliquid products. The latter have a higher hydrogen to carbon ratio thanthe crude petroleum input. By taking high carbon coke as one product,carbon is rejected from the remaining products, thus aiding in balancebetween input and products.

The delayed coking operation is cyclic in nature, operating a battery ofcoke drums which typically may be 18 feet in diameter and 83 feet high.The bottom of the drum is conical, closed at its bottom end by a flangedhead which is removed once in each cycle. At the beginning of a cycle,the drum is heated, as by passing therethrough a portion of the hotvapors from another drum which is in the coking stage. As the drumreaches a suitable temperature, generally in excess of 500F., chargestock from a heater is introduced through a pipe in the bottom head atabout 900F. At this temperature, the heavy stock undergoes thermalcracking to yield light hydrocarbons and coke. Any cracked productboiling below the temperature in the drum, say 880F., will vaporize andis taken overhead through a vapor pipe in the top of the drum torecovery equipment for separation of products such as naphtha, kerosine,light and heavy gas oils as desired.

After about 24 hours, the drum is substantially full of porous coke inwhich the pores are filled with oil. Steam is then introduced throughthe bottom inlet to quench the coke. This achieves steam distillation ofoil then present in the drum. During the early stage of steaming, themixture of water and oil vapors continues to pass to product recovery asduring the coking stage. Thereafter the effluent from steaming isdiverted to blow-down facilities in which it is condensed andtransferred to settling basins where oil is skimmed from the surface ofthe water.

After steam cooling to about 700750F., water is introduced to the bottomof the coke drum to complete 2 until the drum is completely filled withliquid water. For a period thereafter, water is introduced to overflowthe drum with effluent sent to settling equipment for removal ofentrained oil etc.

The water settling system also receives water from other operations inthe coker' facility as later described. The clarified water so obtainedprovides the water for quench and for recovery of coke from the drum.Coke recovery proceeds by removal of top and bottom heads from the drumand cutting of the coke by hydraulic jets. First, a vertical hole isdrilled through mass of coke to provide a channel for coke dischargethrough the bottom opening into a rail car spotted under the drum. Thena hydraulic jet is directed against the upper surface of the coke at adistance from the central discharge bore. The jet moves in a circleabout the bore to cut the coke into pieces and then in larger concentricpaths until a layer is cut away to the side wall. The cutting jet thenrepeats this operation at successive lower levels until the coke bed iscompletely removed.

The coke so cut from the drum appears in all sizes from large lumps tofine particles. To a considerable extent, the fines are separated fromlarger pieces as the coke discharges into hopper cars and water drainsoff through the hopper gates. This dispersion of fines in water ishandled to recover the fines as solid fuel and the water returns to thesystem for use in quenching and cutting. It will be seen that the watercycle is a closed system in the sense that material added thereto mayleave the coker installation only with the coke or with the liquidhydrocarbons produced by thermal cracking in the coke drums.

Sludge Disposal.

Modern manufacturing operations and modern methods for disposal ofsanitary waste result in some materials'which are extremely difficult toconvert into innocuous or useful (recycled) substances at reasonablecost. A major problem of this nature is posed by mixtures which containwater and combustible, fine solids. Such mixtures are often calledsludge and that term will be used herein for designation of materialstreated by the technique of this invention.

Finely divided solids in liquids produce very stable dispersions and arealso very effective stabilizers for liquid/liquid dispersions.

A typical sludge is that derived from activated sewage treatment plantswhich generally discharge an effluent of one weight percent solids.Dewatering techniques are known for concentrating the sludge but theseare expensive and, at best, leave a concentrated sludge of high watercontent.

Petroleum refinery sludges are dispersions of oil and water havinggreatly different proportions of the two immiscible liquids stabilizedby finely divided solids such as silt, sand, rush-high carbon contentcombustibles and the like. Such dispersions are not readily susceptibleto emulsion breaking techniques.

These and other sludges have been subjected to various disposaltechniques at considerable expense and less than uniform satisfaction.Incineration of waste containing substantial amounts of water requireselaborate and expensive equipment. The necessary washing of incineratorstack gases has the result that the end product is still a dispersion ofsolids in water, i.e. a sludge.

Land Farming" is a technique for working sludges into land to permitfinal disposal by the slow process of bacterial action.

SUMMARY OF THE INVENTION It has now been demonstrated that sludges canbe introduced as part of the water quench to hot coke in a delayedcoker. The first tests of this concept were conducted very carefully andunder rigid control to permit immediate termination of the test in theevent increased back pressure against the pumps or other extremevariations in operating parameters should indicate that solids releasedfrom dispersion or oil released from emulsification were accumulating atlocalized points to inhibit flow through the coke bed or produceextremevariation in coke quality. Such adverse result would not besurprising in a system in which the first portions are subjected to suchtemperature that water is immediately flashed off.

No untoward deviations were noted during tests. Sampling of the coke asremoved showed only minor variations in ash and volatile matter in thecoke during cutting at different levels in the bed. In should be notedhere that the commercial scale coker in which the tests were conductedis not susceptible to accurate sampling without serious departures fromnormal operation. The results have been deemed adequate for futureplanning of commercial operation and the added expense of data capableof material balance has not been incurred. With caveat that the datahere reported are not suitable for rigorous analysis of the operation,the data actually obtained are set out below as establishing validity ofgeneralizations expressed.

DESCRIPTION OF PREFERRED EMBODIMENTS The process of the invention isadvantageously carried out in conventional delayed coker equipment,elements of which important to the invention are shown in the annexeddrawing, consisting of a single FIGURE.

In the embodiment illustrated diagrammatically in the drawing, a singlefractionating column (the combination tower) receives both fresh feed tothe unit and vaporized overhead from the coking drum. Fresh feed,supplied by line 11 is any heavy petroleum fraction, such as residuumfrom crude fractionation, heavy recycle stock from catalytic crackingand the like. Generally, such stocks have boiling ranges above about750F. Desired products are separated in the combination tower 10. Asindicated these may be heavy coker gas oil boiling above about 650F.,withdrawn at line 12; light coker gas oil boiling about 400650F., atline 13; and unstabilized gasoline (naphtha and lighter gaseousproducts) at line 14.

A heavy bottoms fraction heavier than gas oil is transferred from thecombination tower 10 by line 15 to pump 16, from which it passes throughfurnace 17 to be heated, for example to about 900F. The heated charge ispassed by line 18 and valve 19 to the inlet 20 to coke drum 21. The drumis one of a plurality, at least two, of such drums. By operating abattery of such drums in series, the system achieves continuousoperation of the combination tower 10 and furnace 17; the hot chargebeing diverted to another drum in the battery when it is desired todischarge coke from a drum which has become full of coke on completionof the reaction stage of its cycle.

In drum 21, the hot oil undergoes an extended period of thermalcracking, often called soaking. That cracking results in formation ofvolatile cracked products and coke. The material which is volatile atthe temperature of the drum is withdrawn at discharge port 4 22. Valve23 being open, the volatile products pass by line 24 to combinationtower 10.

As the reaction stage is concluded, typically after about 24 hours, thedrum 21 contains a body of porous coke having the pores filled by aheavy oil boiling above the temperature of the drum, usually about 880F.Valve 19 is now closed and steam is admitted to inlet 20 by openingvalve 25 in the steam supply line. Steam distillation occurs to removemost of the heavy oil'in drum 21. In the typical embodiment beingdescribed, a first stage of steaming is conducted for 1.5 hours at 4000pounds of steam per hour with valve 23 in open position, whereby thesteam and oil vapors are transferred to the combination tower 10,together with cracked vapor from another drum then in the reactionstage. At the end of the first steaming stage, valve 23 is closed, andvalve 26 in line 27 to the blow-down system is opened. The rate of steamis then increased to 15,000 pounds per hour and maintained at this levelfor 1.5 hours. As will be seen from the drawing, drum effluent duringthe second steaming stage passes through a condenser 28 and passes asliquid to settling basin and skimmer 29. The oil content of the drumeffluent rises to the top of the water in skimmer 29 and is removed byusual skimming techniques to be recycled through line 32 to the feedline 11 of combination tower 10. Water from skimmer 29 is transferred byline 31 to clear water tank 32 for use as hereinafter described.

At the termination of the second steaming stage, the bed of coke is at atemperature of about 700750F. Valve 25 is now closed and valve 33 isopened to permit entry to the coke drum of water drawn from clear watertank 32 by pump 34. Water so admitted is converted to steam in coolingthe coke and the so generated steam passes by valve 26 to the blow-downsystem for return to the clear water tank. As the coke reaches thetemperature of the water, water fills the voids in the bed of coke. Theflow from the top of the drum may then be diverted directly to skimmer29 by closing valve 26 and opening valve 45 to line 46 which bypassesthe condenser 28. After liquid water has been flowed through the cokelong enough to ensure adequate cooling, the drum is ready to be decoked.

Decoking proceeds by removal of flanged heads from top and bottom of thedrum and cutting the coke by hydraulic jets. A railroad hopper car,indicated generally at 35, spotted below the drum, receives coke as itis discharged from the drum. The first stage of decoking is accomplishedby drilling a bore through the center of the coke to provide a dischargechannel. The hydraulic jet, not shown, is returned to the top of thedrum after cutting the bore. It is then directed against the top of thecoke while moving in a circular path concentric with and outside thebore. This cuts away lumps of coke which descend with water through theopen bottom of the drum and into the hopper car 35. Water flows out ofthe bottom of the car 35 through the gaps at the hopper gates to bereceived in a sump lined with concrete 36 below the rail 37 and ties 38on which the car 35 is supported. The water, which contains fineparticles of coke, passes by line 39 to clarification equipmentindicated generally at 40. Clear water from clarification is returned byline 41 to clear water tank 32.

In applying the invention to this conventional delayed coking operation,a sludge is added to the cooling water by a pump 42 through valve 43.The sludge preferably is supplied during that stage of water coolingwhen the coke is hot enough to vaporize the cooling It is found thatsanitary sludges are handled to best advantage at the earlier stages ofwater cooling, while the coke is a high temperature, e.g., above about500F. Where sludges of both biological and oily types are .to behandled, it is preferred that the biological waste from activated sewagetreatment be injected with the first cooling water and oily sludge addedlater, total injection being completed before the coke becomes coolenough to begin filling of voids. Later injection will achieve some ofthe advantages of the invention but risks discharge of stubbornsuspensions to the clear water tank. As will appear from data below, thestubborn suspensions are broken on hot coke with deposition of organicand solid components of the sludge on the coke, usually withoutexceeding specification limits for metallurgical coke, namely 15.0 wt.%volatile at 1800F., 0.5 wt.% ash. As will be readily apparent, coke tobe used as furnace fuel is subject to much more liberal specifications.

A series of five test runs were conducted under conditions 'of normaloperation of the coke drum as described above. In each test run,contaminants were introduced with the cooling water under conditionssuch that temperature of the top of the coke bed was above 450F., at theend of the test run. The test runs included operations in which anormally oily sludge from refinery operation and a normal biologicalsludge were used. The tests also included materials which are not normalsludges to evaluate effect of high concentrations of inorganic solidsand hydrocarbons. The test runs are described in the examples below. Ineach case, water injection and decoking were normal.

EXAMPLE 1 The sludge in this example was a refinery slop emul sioncontaining 48 weight percent water. Hydrocarbon content consisted of46.6 weight percent extractable by normal heptane (arbitrarily calledoil) and 1.2 weight percent soluble in toluene (asphalt). The residualsolids after drying and extraction with normal heptane and toluene hadthe following analysis:

Volatile at 1800F. 2.4 wt.%

Fe O 0.4 FeSO, 0.5 SiO 1.0

During introduction of 50 barrels of water from the clear water tank atstart of the water quench stage, 50 barrels of the above slop emulsionwere metered into the cooling water. Flow of cooling water was normal,without indication of unusual back pressures against the pumps. Sampleswere taken of coke during the cutting operation. While there is no wayto be assured that coke delivered is entirely derived from the level atwhich cutting occurs, results in this and other test runs is good groundfor confidence in the values reported, in that averages are all withinspecification values for metallurgical coke.

A sample taken during cutting of the top /a of the drum showed a VCM(Volatile Combustible Material at 1800F.) of 10.2 wt.%. Sample takenduring cutting at the bottom A; of the drum showed 8.9 wt.% VCM.

EXAMPLE 2 In this test, the same slop emulsion was injected as inExample 1; but at double the quantity, i.e., 100 barrels.

6 Inspection of coke during cutting showed average co ke quality withinspecification:

Middle l/3 Bottom l /3 Bottom 111.8 10.8 18.5 11.8 Average 13.2

EXAMPLE 3 QUALITY Top H3 140 0.26 0.04

Middle l/3 8.5 0.13 0.02

Bottom l/3 9.9 0.21 0.015

Bottom 13.5 0.47 0.11 Average 1 1.5 0.27 0.05

EXAMPLE 4 Biological sludge (sanitary waste) from activated sludgetreatment of refinery effluent water was dewatered to about 6 wt.%solids. Fifty barrels of the dewatered biological sludge were added toquench water to the coke drum. Injection was normal. The coke was withinspecifications for metallurgical coke:

1 1.3 Middle H3 110 Bottom 1]} 11.5 Bottom Head 20.0

Average 13.5

EXAMPLE 5 This test run was with a synthetic sludge containing a mixtureof possibly troublesome materials to severely test the technique of thisinvention. The synthetic sludge was constituted by 50 barrels of waxemulsion (50% paraffin wax), 3000 pounds of powdered barytes, 7000pounds of fine catalyst rejected from a Fluid Catalytic Cracker becauseof fineness, barrels of water and 50 barrels of the dewatered biologicalsludge described in Example 4. Again, quenching and decoking proceedednormally. The coke showed abnormally high ash content with this abnormalsynthesized sludge. Of particular interest is the distribution of ash:

It will be seen that the invention provides a method for disposing ofstubborn dispersions such as biological sludge and oily sludge. Theseare characterized 'by finely dispersed solids and combustible matter. Inthe case of oily sludges, the dispersed solids are often noncombustiblewhich become ash distributed through the coke product. The solids insome oil sludges may be themselves largely combustible. For example, ina refinery scheme which includes catalytic cracking of coker gas oilsand coking of bottoms fraction from catalytic cracking can result incompounds of very low hydrogen/carbon ratio having a density greaterthan that of water. These can pass to the skimmer and there form asludge with coke fines at the bottom of the skimmer. Such verytroublesome sludges can be handled to good advantage by mixture with thecoker quench water as described above.

The biological sludges have dispersed'solids which are the combustiblematter there present.

I claim:

l. A new use for a delayed coker in addition to its known operationwherein a body of hot liquid oil is maintained at thermal crackingtemperature in an enlarged vessel for an extended period of time withdischarge of cracked vapors for recovery of cracked product andaccumulation of solid, porous coke in the vessel, whereupon the coke issteamed to reduce its tem- 8 perature and liquid water is introduced tothe coke to quench it to temperature at which it may be recovered,

' initially at a coke temperature hot enough to vaporize the water andfinally at a coke temperature such that water fills voids in the coke;

said new use comprising addition to said liquid water I during theinitial stage of coke temperature hot enough to vaporize the water ofliquid sludge which contains dispersed combustible matter and finelydispersed solid particles which may be the said combustible matter;whereby the dispersion is broken with incorporation of combustiblematter therefrom in the coke while conducting quenching and recovery ofsaid coke.

2. A new use defined in claim 1 wherein said sludge is biological sludgefrom activated sludge treatment of waste water effluent.

3. A new use defined in claim 1 wherein said sludge is an oily emulsionwith water stabilized by finely dispersed solids.

4. A new use according to claim 1 wherein water introduced to said cokeis collected after contact with said coke to provide a source of liquidwater to be introduced as aforesaid.

1. A NEW USE FOR ADELAYED COKER IN ADDITION TO ITS AKNOWN OPERATIONWHEREIN A BODY OF HOT LIQUID OIL IS MAINTAINED AT THERMAL CRACKINGTEMPERATURE IN AN ENLARGED VESSEL FOR AN EXTENDED PEROID OF TIME WITHDISCHARGE OF CRACKED VAPORS FOR RECOVERY OF CRACKED PRODUCT ANDACCOMULATION OF SOLID, POROUS COKE IN THE VESSEL, WHEREUPON THE COKE ISSTEAMED TO REDUCE ITS TEMPERATURE AND LIQUID WATER IS INTRODUCED TO THECOKE TO QUENCH IT TO TEMPERATURE AT WHICH IT MAY BE RECOVERED, INITIALLYAT A COKE TEMPERATURE HOT ENOUGH TO VAPORIZE THE WATER AND FINALLY AT ACOKE TEMPERATUE SUCH THAT WATER FILLS VOIDS IN THE COKE, SAID NEWCOMPRISING ADDITION TO SAID LIQUID WATER DURING THE INITIAL STAGE OFCOKE TEMPERATURE HOT ENOUGH TO VAPORIZE THE WATER OF LIQUID SLUDGE WHICHCONTAINS DISPERSED COMBUSTIBLE MATTER AND FINELY DISPERSED SOLIDPARTICLES WHICH MAY BE THE SAID COMBUSTIBLE MATTER, WHEREBY THEDISPERSION IS BROKEN WITH INCORPORATION OF COMBUSTIBLE MATTER THEREFROMIN THE COKE WHILE CONDUCTING QUENCHING AND RECOVTERY OF SAID COKE.
 2. Anew use defined in claim 1 wherein said sludge is biological sludge fromactivated sludge treatment of waste water effluent.
 3. A new use definedin claim 1 wherein said sludge is an oily emulsion with water stabilizedby finely dispersed solids.
 4. A new use according to claim 1 whereinwater introduced to said coke is collected after contact with said coketo provide a source of liquid water to be introduced as aforesaid.